Double loop heater

ABSTRACT

An apparatus comprises a slider comprising an air bearing surface (ABS). The slider comprises a reader, a writer, and a reader heater. The reader heater is configured to cause a protrusion of the ABS proximate the reader, and the reader heater comprises a first planar loop and a second planar loop, wherein the first and second loops are in the same plane.

SUMMARY

Embodiments of the disclosure are directed to an apparatus comprising aslider having an air bearing surface (ABS). The slider comprises areader, a writer, and a reader heater configured to cause a protrusionof the ABS proximate the reader. The reader heater comprises a firstplanar loop and a second planar loop, wherein the first and second loopsare in the same plane.

Further embodiments are directed to an apparatus comprising a sliderhaving an air bearing surface. The slider comprises a reader, a writer,and a reader heater configured to cause a protrusion of the ABS at thereader. The reader heater comprises a first loop having a first shapeand a second loop having a second shape different from the first shape.The first and second loops are coplanar.

Additional embodiments are directed to an apparatus comprising a sliderhaving an air bearing surface (ABS). The slider comprises a reader, awriter, and a reader heater configured to cause a protrusion of the ABSproximate the reader. The reader heater has a symmetrical shape about anaxis of symmetry perpendicular to the ABS, and the reader heatercomprises a first planar loop and a second planar loop wherein the firstand second loops are in the same plane.

The above summary is not intended to describe each disclosed embodimentor every implementation of the present disclosure. The figures and thedetailed description below more particularly exemplify illustrativeembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The discussion below refers to the following figures, wherein the samereference number may be used to identify the similar/same component inmultiple figures. However, the use of a number to refer to a componentin a given figure is not intended to limit the component in anotherfigure labeled with the same number. The figures are not necessarily toscale.

FIG. 1 is a perspective view of a HAMR slider assembly according toembodiments discussed herein;

FIG. 2 is a cross-sectional view of a slider along a down-track plane,according to embodiments discussed herein;

FIG. 3A is a plan view of a double loop reader heater according toembodiments discussed herein;

FIG. 3B is a plan view of a double loop reader heater according toembodiments discussed herein;

FIG. 3C is a plan view of a double loop reader heater according toembodiments discussed herein;

FIG. 4A is a contour view of contact area for the double loop readerheater of FIG. 3A;

FIG. 4B is a contour view of contact area for the double loop readerheater of FIG. 3B;

FIG. 4C is a contour view of contact area for the double loop readerheater of FIG. 3C;

FIG. 4D is a contour view of contact area for a single loop readerheater;

FIG. 5A is an elevation profile of a slider ABS where the sliderincludes the double loop reader heater of FIG. 3A;

FIG. 5B is an elevation profile of a slider ABS where the sliderincludes the double loop reader heater of FIG. 3B;

FIG. 5C is an elevation profile of a slider ABS where the sliderincludes the double loop reader heater of FIG. 3C;

FIG. 5D is an elevation profile of a slider ABS where the sliderincludes a single loop reader heater;

FIG. 6 is a plan view of a double loop reader heater according toembodiments discussed herein;

FIG. 7A is a contour view of contact area for a single loop readerheater;

FIG. 7B is a contour view of contact area for the double loop readerheater of FIG. 6;

FIG. 8A is a downtrack elevation profile of a slider ABS where theslider includes a single loop reader heater;

FIG. 8B is a downtrack elevation profile of a slider ABS where theslider includes the double loop reader heater of FIG. 6;

FIG. 9A is a crosstrack elevation profile of a slider ABS where theslider includes a single loop reader heater; and

FIG. 9B is a crosstrack elevation profile of a slider ABS where theslider includes the double loop reader heater of FIG. 6.

DETAILED DESCRIPTION

The present disclosure is generally related to magnetic recording, andmore specifically, reading magnetically recorded data. A read/writeelement, sometimes referred to as a slider, recording head, read head,write head, read/write head, etc., includes magnetic read and writetransducers. For example, a magnetoresistive sensor reads data bydetecting magnetic fluctuations of a magnetic media as it movesunderneath the sensor. The reader components described herein (e.g.,reader heater) are applicable to various magnetic recording techniquesincluding perpendicular magnetic recording and heat-assisted magneticrecording (HAMR). However, as certain embodiments are directed toaddressing factors associated with HAMR, HAMR is discussed in moredetail below.

HAMR is also referred to as energy-assisted magnetic recording (EAMR),thermally-assisted recording (TAR), thermally-assisted magneticrecording (TAMR), etc. In a HAMR device, a source of optical energy(e.g., a laser diode) is integrated with a recording head and couplesoptical energy to a waveguide or other light transmission path. Thewaveguide delivers the optical energy to a near-field transducer (NFT).The NFT concentrates the optical energy into a tiny optical spot in arecording layer of a magnetic recording medium, which raises themedium's temperature locally, reducing the writing magnetic fieldrequired for high-density recording.

The magnetic read and write transducers of a HAMR slider are similar tothose used in other hard drives, e.g., perpendicular recording drives.Data is written to the magnetic media by a write coil that ismagnetically coupled to a write pole. The write pole changes magneticorientation in regions of the media as it moves underneath the writepole in response to an energizing current applied to the write coil. AHAMR slider also includes a source of energy, such as a laser diode, toheat the media while it is being written to by the write pole. Anoptical delivery path, such as a waveguide, is integrated into the HAMRslider to deliver the energy to the surface of the media.

The optical delivery path of a HAMR slider may include a plasmonictransducer proximate a media-facing surface (e.g., air-bearing surface(ABS), contact surface). The plasmonic transducer shapes and transmitsthe energy to a small region on the medium. The plasmonic transducer issometimes referred to as a NFT, optical antenna, surface plasmonresonator, etc., and may include a plasmonic metal such as gold, silver,copper, aluminum, etc., and alloys thereof. The plasmonic transducer fora HAMR device is very small (e.g., on the order of 0.1 to a few lightwavelengths, or any value therebetween) and creates a localized regionof high power density in the media through an electromagneticinteraction. This results in a high temperature rise in a small regionon the media, with the region reaching or exceeding the Curietemperature (T_(c)) and having dimensions less than 100 nm (e.g., ˜50nm).

The heat generated during write operations can cause portions of theABS, typically portions near the NFT and waveguide, to expand. Thermalresistive sensors can be positioned in/near this expansion area todetect whether the ABS contacts the recording media. Similarly, heat isgenerated during read operations to create a protrusion in the ABSthereby moving the read sensor element closer to the recording medium toimprove the strength and reliability of the read signal. While a widercontact area provides a more controlled head to media spacing (and amore reliable read signal), it can also increase the temperature of theread sensor element due to slower heating and burnishing upon contactwith the recording medium. Thus, the size of the contact area needs tobe configured with respect to the temperature of the reader. Embodimentsherein are directed to achieving a balance between the size/shape of thecontact area and the read sensor element temperature using the shape ofa reader heater. The heat that forms the ABS protrusion at the reader isgenerated by a reader heater.

The heater is positioned within the slider (e.g., recessed from the ABS)and proximate the read sensor element at the ABS. Using current readerheater designs having a single loop projecting toward the ABS, thehigher the heater temperature, the lower the corresponding temperatureof the read sensor element is. Also, the resistance of the reader heateris constrained by the pre-amp limit for the total circuit (heater,traces, and TGA), which is about 40-55 ohms. Using a dual parallel loopreader heater design reduces the electrical resistance of the heater aswell as the temperature. Notably, the dual loop heater designs describedherein generate a lower read sensor element temperature when generatinga lower reader heater temperature. This is because current density isspread around the loops by dividing the input current into two differentpaths and the heat density is spread across more area. In certainembodiments, the dual loops also provide increased control over thecontact area as one loop is designed to address stroke efficiency, andthe other loop is designed to address the size/shape of the contactarea. Although the dual loop reader heater designs may be used for anytype of magnetic recording head, including perpendicular recording, theyare described herein in the context of a HAMR slider.

With reference to FIG. 1, a perspective view shows a HAMR sliderassembly 100 according to a representative embodiment. The sliderassembly 100 includes a laser diode 102 located on input surface 103 ofa slider body 101. In this example, the input surface 103 is a topsurface, which is located opposite a media-facing surface 108 that ispositioned over a surface of a recording media (not shown) during deviceoperation. The media facing surface 108 faces, and is held proximate to,the moving media surface while reading and writing to the media. Themedia-facing surface 108 may be configured as an air bearing surfacethat maintains separation from the media surface via a thin layer ofair.

The laser diode 102 delivers light to a region proximate a HAMRread/write head 106, which is located near the media-facing surface 108.The energy heats the recording media as it passes by the read/write head106. Optical coupling components, such as a waveguide system 110, areintegrally formed within the slider body 101 (e.g., near a trailing edgesurface 104 of the slider) and function as an optical path that deliversenergy from the laser diode 102 to the recording media via a NFT 112.The NFT 112 is proximate the writer of the read/write head 106 andcauses heating of the media during recording operations.

The laser diode 102 may be configured as either an edge-emitting laseror surface-emitting laser. While the representative embodiment in FIG. 1shows a laser diode 102 directly mounted to the slider body 101, thewaveguide system 110 discussed herein may be applicable to any type oflight delivery configuration. For example, a laser may be mounted on thetrailing edge surface 104 instead of the top surface 103. In anotherconfiguration known as free-space light delivery, a laser may beexternally mounted to the slider 100, and coupled to the slider by wayof optic fiber and/or a waveguide. An input surface of the slider body103 may include a grating or other coupling feature to receive lightfrom the laser via the optic fiber and/or waveguide. The slidercomponents proximate the air bearing surface (ABS) 108 are discussedfurther below.

In FIG. 2, a cross-sectional view illustrates portions of the sliderbody 200 near the media-facing ABS 201 in further detail according tovarious embodiments. A writer 202 includes a number of components,including a second return pole 203 proximate a write coil 204. The writecoil 204 includes an upper coil 205 and a lower coil 206. The write coil204 may conform to any writer coil design, including a double-pancakedesign, single-layer pancake design, or a helical coil design, forexample.

The write coil 204 is configured to energize a write pole 208. Amagnetic yoke 207 is disposed between the write coil 204 and the writepole 208. A write pole heat sink 209 is thermally coupled to the writepole 208. A writer heater 210 is positioned proximate the write pole 208and is configured to thermally actuate the write pole 208 during writeoperations. An NFT 212 is situated proximate the write pole 208 and isoptically coupled to an optical waveguide 214. The waveguide 214includes an upper cladding layer 215, a lower cladding layer 217, and acore 219 between the upper and lower cladding layers 215, 217. Adiffuser 213 thermally couples to the NFT 212 and extends between atleast a portion of the write pole 208 and the upper cladding layer 215.The writer 202 also includes a leading shield 225 and a first returnpole 216, which is magnetically coupled to the write pole 208 and thesecond return pole 203.

The slider 200 also includes a reader 218. The reader 218 includes aread element 224 (e.g., a GMR sensor) disposed between a pair of readershields 221, 223. A reader heater 230 is located proximate the reader218, which is configured to thermally actuate the reader 218 during readoperations. The reader heater 230 is a dual loop heater having a firstloop 232 and a second loop 234. Proximate the reader heater 230 is apush block 236, which helps control the shape and actuation efficiencywithin the slider 200 by distributing the heat generated by readerheater 230. The push block 236 distributes heat to the reader shields221, 223, causing them to protrude toward the ABS 201, and toward arecording medium to create a protrusion 228. The protrusion 228 cancreate a corresponding contact area of the ABS 201 that contacts themedium.

The slider 200 includes several sensors. For example, a contact sensor211 may be positioned at or near the ABS 201 in the waveguide cladding217. At this location, the contact sensor 211 is arranged to detectcontact between a close point of the writer 202 (when thermally actuatedby one or more heating elements) and a magnetic recording medium. Theslider 200 also includes a contact sensor 227 positioned proximate thereader 218. The contact sensor 227 is configured to detect contactbetween a close point of the reader 218 (when thermally actuated by oneor more heating elements) and the recording medium. In some embodiments,the writer contact sensor 211 is coupled (in series or in parallel) tothe reader contact sensor 227. In other embodiments, the writer andreader contact sensors 211 and 227 are independent of each other.

The contact sensors 211, 227 are typically thermal sensors having atemperature coefficient of resistance (referred to herein as TCRsensors, such as a differential-ended TCR sensor or DETCR). A DETCRsensor is configured to operate with each of its two electrical contactsor leads (ends) connected to respective bias sources provided by a pairof electrical bond pads of the slider. According to various embodimentsdescribed herein, the thermal sensor may be referred to as a contactsensor, a thermal asperity sensor, a laser power monitor, and/or aDETCR. The TCR sensors 211, 227 are configured to sense changes in heatflow for detecting onset of head-medium contact. Thus, the readercontact sensor 227 is positioned within the protrusion area 228 andproximate the read element 224. The reader heater 230, which generatesheat flow proximate the reader and the protrusion area 228, is describedfurther below.

FIGS. 3A-C illustrate double loop reader heater configurations accordingto various embodiments. As discussed above, a dual branch (or loop)heater design reduces the resistance of a reader heater. In certainembodiments, the dual loops have a parallel resistor configuration andare typically used in HAMR recording. As shown in FIG. 3A, a readerheater 300 comprises a first loop 302 positioned around a second loop304 such that the second loop 304 is located within the first loop 302.While the reader heater 300 is a three-dimensional element of theslider, the heater 300 as well as both of the first and second loops302, 304, are planar (i.e., flat and lying in one plane) and both thefirst and second loops 302, 304 are positioned in the same plane. Theloops 302, 304 create an open space between them 306. The parallel loops302, 304 are also symmetrical about an axis 322 substantiallyperpendicular to the ABS. Thus, a left portion 324 of FIG. 3A is shownas a mirror image of a right portion 326. In certain embodiments, theaxis of symmetry 322 is positioned substantially centered over the readelement of the slider.

The reduction in resistance occurs due to the division of the currentsupplied to the reader heater 300 into two paths through the first andsecond loops 302, 304, respectively. A first path is illustrated byarrow 308 showing input current to the first loop 302 and arrow 310showing current exiting the first loop 302. The second path isillustrated by arrow 312 showing current input to the second loop 304and arrow 314 showing current exiting the second loop 304. The heaterconfiguration of FIG. 3A has a resistance of about 56 ohms where theline width, shown by arrow 320, is about 3 micrometers. While thecombination of the first and second loops 302, 304 affects theresistance of the heater, the individual loops provide discrete controlover other factors. For example, the first loop 302 is used to controlthe ABS protrusion contact area. Changing the width 328 of the portion316 proximate the ABS, changes the size and/or shape of the contactarea. The second loop 304 controls the stroke efficiency. The heater ispositioned along a crosstrack direction in the slider such that portion316 is proximate the ABS. For example, if a slider was bisected in adowntrack direction along line of symmetry 322, the first and secondloops would appear consistent with those shown in FIG. 2.

The embodiment shown in FIG. 3B has the same configuration as that ofFIG. 3A, with the exception of a different line width. FIG. 3B also hassecond loop 304 positioned within first loop 302 creating open space306. The double loops are symmetrical about an axis of symmetrysubstantially perpendicular to the ABS and form parallel resistors.However, the line width, shown by arrow 320, is about 4 micrometers, andthe resulting heater 330 resistance is about 40 ohms. In addition to areduction in resistance, the wider line width also provides increasedreliability for the reader heater. Along with altering the line width,further embodiments comprise an altered shape of the first loop.

Similar to FIG. 3A, FIG. 3C shows an embodiment of a reader heater 350that comprises a first loop 352 positioned around a second loop 354 suchthat the second loop 354 is located within the first loop 352. Both ofthe first and second loops 352, 354, are planar and both are positionedin the same plane. The loops 352, 354 create an open space between them356. The parallel loops 352, 352 are also symmetrical about an axis 372substantially perpendicular to the ABS. Thus, a left portion 374 of FIG.3C is shown as a mirror image of a right portion 376. In certainembodiments, the axis of symmetry 372 is positioned substantiallycentered over the read element of the slider.

The reduction in resistance occurs due to the division of the currentsupplied to the reader heater 350 into two paths through the first andsecond loops 352, 354, respectively. A first path is illustrated byarrow 358 showing input current to the first loop 352 and arrow 360showing current exiting the first loop 352. The second path isillustrated by arrow 362 showing current input to the second loop 354and arrow 364 showing current exiting the second loop 354. A differencebetween the heater configuration of FIG. 3A and that of FIG. 3C is theshape of the first loop 352. Both configurations include a portion 316,366 oriented in the crosstrack direction in the slider, proximate theABS, and have the same shape. Also, the first loops 302, 352 of bothconfiguration extend away from the ABS at the ends of the ABS portion316, 366. However, in FIG. 3C, the first loop 352 includes a portionthat then extends substantially parallel to the ABS, back toward thecenter of the heater (i.e., toward the axis of symmetry 372). This formsan indentation, indicated by arrow 380, in the sides of the heater. Theindentation is also formed by a taper in the sides of the heater as theyextend away from the ABS. The angle of the taper affects the amount ofmaterial forming the heater and therefore at least in part affects theheater's resistance. While the heater configuration of FIG. 3C has aline width, shown by arrow 370, of about 4 micrometers, the heater 350has a resistance of about 44 ohms.

In addition to an improvement (i.e., reduction) in resistance, doubleloop reader heater configurations provide further advantages incomparison with a single loop heater. For example, stroke efficiency,various temperatures, and GammaCP may be compared among the variousconfigurations. Gamma CP is the ratio between the transducer's closepoint movement during heat activation relative to the reader's movement.For example, if the ratio is 1, the reader is the close point since bothare moving the same and coincident. If the ratio is greater than 1, theclose point is closer to the trailing edge and the reader is slightlyrecessed. The opposite is the case if the ratio is less than 1. Thefollowing table (Table 1) provides various test parameters for thedouble loop configurations shown in FIGS. 3A-C as compared with a singleloop configuration (e.g., a knife configuration).

TABLE 1 Parameter (unit) Single Loop FIG. 3A FIG. 3B FIG. 3C StrokeEfficiency (A/mW) 1.40 1.1 1.09 1.09 GammaCP (ratio) 1.01 1.02 1.02 1.02Htr Temp Rise Rate (° C./Å) 2.30 1.66 1.60 1.65 Rdr Temp Rise Rate (°C./Å) 0.29 0.29 0.29 0.29 ABS Temp Rise Rate (° C./Å) 0.30 0.32 0.310.31 Projected Rdr Temp 109 108 108 107 @Hot (° C.) Projected Htr Temp416 312 303 310 @Hot (° C.) Contact Area (μm²) 11.1 23.1 22.3 21.6 RHTPTC (mW) 110.2 135.0 136.0 136.5 RHT Resistance (Ω) 36 56 40 44The double loop heater configurations of FIGS. 3A-C provide comparableresults for the heater resistance in comparison with a knife (singleloop of Table 1) configuration and significant reductions in resistancewhen compared to other single loop configurations (e.g., configurationshaving a width of the portion proximate the ABS similar to that of FIGS.3A-C). The table indicates that the double loop configurations willpotentially reduce stroke efficiency since the heat sources are furtheraway from the transducer crosstrack centerline. The heater temperaturerise rate is dramatically improved with the double loop heaterconfigurations while the reader/ABS temperature rise rates remain flat.As discussed above, reducing the reader temperature is an importantdesign parameter, and the double loop configurations provide acomparable reader temperature rise rate but a significant reduction inheater temperature (Projected Htr Temp @Hot) as compared with the singleloop configuration. Also, the contact area increases dramatically withthe double loop heater configurations.

Another important design parameter is the size and shape of the contactarea generated by the reader heater by protruding the ABS. FIGS. 4A-Dare contour diagrams showing the contact area created by variousembodiments of an activated reader heater. Each of the diagrams showsthe clearance (head to media spacing)/protrusion from the ABS in boththe crosstrack and downtrack directions. Several components at the ABSare identified in FIG. 4A, and the same labels apply to each of FIGS.4A-D. From left-to-right in each diagram are the reader shields 423, thereader contact sensor 427, the first return pole 416, the NFT and writepole tip 412, another contact sensor 411, and the second return pole403.

FIG. 4A shows the contact area for a double loop heater configuration asshown in FIG. 3A. Here the contact area extends in the crosstrackdirection, has a central portion with a clearance of about 2.9 nm, andis primarily located proximate the first return pole 416. FIG. 4B showsthe contact area for a double loop heater configuration as shown in FIG.3B. The contact area also extends in the crosstrack direction, has aslightly smaller central portion with a clearance of about 2.9 nm, andis primarily located proximate the first return pole 416. FIG. 4C showsthe contact area for a double loop heater configuration as shown in FIG.3C. The contact area again extends in the crosstrack direction, has aslightly less consistently shaped central portion with a clearance ofabout 2.9 nm, and is primarily located proximate the first return pole416. For comparison, FIG. 4D shows the contact area for a single loopheater having a knife configuration. Here the contact area is smallerand more focused, has a central portion with a smaller clearance ofabout 2.7-2.8 nm, and extends across the first return pole 416, thereader contact sensor 427, and the reader shields 423. The contourdiagrams illustrate how the width of a first/external loop of a doubleloop heater influences both the size and shape of the contact area ascompared with a narrow (i.e., knife) shaped single loop heater design.

The differences in contact areas for the respective configurations arefurther illustrated in the elevation profiles of FIGS. 5A-D. Each of theelevation profiles of FIGS. 5A-D illustrate the same slider componentsproximate the ABS that are labeled in FIG. 5A. From left-to-right, thecomponents in the downtrack direction are the slider substrate 502, basecoat 504, reader shields 523, reader contact sensor 527, first returnpole 516, the NFT and pole tip 512, a writer contact sensor 511, and thesecond return pole 503. FIG. 5A shows the size and shape of theprotrusion/contact area for a slider having a reader heater as shown inFIG. 3A. FIG. 5B shows the size and shape of the protrusion/contact areafor a slider having a reader heater as shown in FIG. 3B. FIG. 5C showsthe size and shape of the protrusion/contact area for a slider having areader heater as shown in FIG. 3C, and FIG. 5D shows the size and shapeof the protrusion/contact area for a slider having a single loop heaterwith a knife configuration. In addition to the change in clearance amongthe various configurations, the close point of the contact area alsomoves as a function of the reader heater configuration when the readerheater is activated. The close point is the position on the protrudedABS that is closest to the recording medium. The close point of a slidercan vary depending on which, how many, proximity to the ABS for, or theamount of power supplied to, heat-generating elements that areactivated. In addition, the use of materials having high coefficients ofthermal expansion such as copper, silver, and 20/80 NiFe can aid inclose point control if a heater is used in close proximity.

Another way to control the size/shape of the contact area is to use analternative reader heater configuration. FIG. 6 illustrates a doubleloop reader heater with dual loops providing two resistors in parallel.These configurations may typically be used in perpendicular magneticrecording and provide similar advantages as described for the dual loopheater configurations above. The first loop 602 and the second loop 604are side by side instead of the nested configurations of FIGS. 3A-C.However, similar to the double loop configurations of FIGS. 3A-C, thefirst loop 602 and second loop 604 are coplanar. The configurations arealso similar in that they are symmetrical about an axis 622substantially perpendicular to the ABS, and the connection points arelocated on the axis 622. A first half 624 of the reader heater is amirror image of the second half 626. The dual loops also form an openingin the reader heater 606. As discussed above, the line width 618 of thefirst and second loops can be varied to control the resistance of theheater. Also, the distance between the loops 628 (e.g., the close pointsof each loop) can be varied to control the shape of the contactarea/protrusion.

Similar to the nested dual loop heater configurations of FIGS. 3A-C, thedual loop heater configuration of FIG. 6 provides operational advantagesover a single loop read heater configuration. The following table (Table2) provides various test parameters for the double loop configurationshown in FIG. 6 as compared with a single loop configuration (i.e., abaseline configuration).

TABLE 2 Parameter (unit) Single Loop FIG. 6 Stroke Efficiency (A/mW) 1.21.17 GammaCP (ratio) 1.00 1.00 Htr Temp Rise Rate (° C./Å) 2.0 1.61 RdrTemp Rise Rate (° C./Å) 0.40 0.37 ABS Temp Rise Rate (° C./Å) 0.41 0.40Projected Rdr Temp 94.2 91.8 @Hot (° C.) Projected Htr Temp 211 182.5@Hot (° C.) Contact Area (μm²) 19 25.5 RHT PTC (mW) 66.4 62.4 RHTResistance (Ω) 43 30.4In addition to improved resistance, the parallel double loop heaterconfiguration of FIG. 6 provides the ability to maintain strokeefficiency, increase contact area, and lower reader temperature whilesignificantly lowering the heater temperature. As suggested above, thecontact area increases as the distance between the loops 628 increases.Stroke efficiency will fall slightly as the distance between the loops628 increases but not enough to significantly impact operability.Varying the line width 618 also influences the heater temperature riserate and the overall temperature. For example, wider loop widths 618(i.e., wider line traces) will reduce the heater temperature and theconsequent temperature rise rate.

The size and shape of the contact area generated by the double loopreader heater of FIG. 6 are shown in the contour diagram of FIG. 7B.This may be compared with the contour diagram of a single loop heaterconfiguration (i.e., the baseline configuration of Table 2) of FIG. 7Ashowing the contact area created by an activated reader heater. Thediagrams show the clearance (head to media spacing)/protrusion from theABS in both the crosstrack and downtrack directions. The reader shields723 and the reader contact sensor 727 of a slider at the ABS areidentified in FIG. 7A, and the same labels apply to the components ofFIG. 7B. While the contact areas for both configurations are similarlypositioned, the contact area of the double loop reader heater of FIG. 7Bis significantly larger in both the crosstrack and downtrack dimensions.Also, the close point, or clearance of the contact area in FIG. 7B islower/closer to the media (e.g., about 2.52 nm).

The differences in contact areas for the two configurations are furtherillustrated in the elevation profiles of FIGS. 8A-B and 9A-B. FIGS. 8Aand 9A illustrate the downtrack and crosstrack, respectively, elevationprofiles for the single loop reader heater configuration of Table 2, andFIGS. 8B and 9B illustrate the downtrack and crosstrack, respectively,elevation profiles for the double loop reader heater configuration ofFIG. 6. The slider substrate 802, base coat 804, reader shields 823, andreader contact sensor 827 proximate the ABS are identified in FIG. 8Aand are the same as the components in FIG. 8B. As discussed above, FIGS.8A-B illustrate that the double loop reader heater has a lowerclearance, and FIGS. 9A-B show that the double loop reader heatergenerates a broader crosstrack profile (i.e., larger contact area) witha similarly located close point as the single loop reader heater profilein FIG. 9A.

As shown and described above, double loop reader heater configurations,both nested and side-by-side, provide reduced resistance whilemaintaining other advantages of currently used single loop reader heaterconfigurations. In addition, a parallel (nested) double loop heaterconfiguration provides individual control over stroke efficiency andcontact area via the discrete loops. Thus, the size/shape of the contactarea can be designed to achieve a balance with the read sensor elementtemperature using a double loop reader heater.

Unless otherwise indicated, all numbers expressing feature sizes,amounts, and physical properties used in the specification and claimsare to be understood as being modified in all instances by the term“about.” Accordingly, unless indicated to the contrary, the numericalparameters set forth in the foregoing specification and attached claimsare approximations that can vary depending upon the desired propertiessought to be obtained by those skilled in the art utilizing theteachings disclosed herein. The use of numerical ranges by endpointsincludes all numbers within that range (e.g. 1 to 5 includes 1, 1.5, 2,2.75, 3, 3.80, 4, and 5) and any range within that range.

The foregoing description of the example embodiments has been presentedfor the purposes of illustration and description. It is not intended tobe exhaustive or to limit the embodiments to the precise form disclosed.Many modifications and variations are possible in light of the aboveteaching. Any or all features of the disclosed embodiments can beapplied individually or in any combination and are not meant to belimiting, but purely illustrative. It is intended that the scope of theinvention be limited not with this detailed description, but rather,determined by the claims appended hereto.

1. An apparatus, comprising: a slider having an air bearing surface(ABS), the slider comprising: a reader; a writer; and a reader heaterconfigured to cause a protrusion of the ABS proximate the reader, thereader heater having first and second tapered sides positioned oppositeeach other in a crosstrack direction, each taper narrowing therespective side in a direction toward the ABS, the reader heater furthercomprising a first planar loop and a second planar loop wherein thefirst and second loops are in the same plane and the first planar loopcomprises a first portion that extends from a first end proximate theABS to a second end proximate the ABS substantially parallel to the ABSand has a central part of the first portion recessed from the first andsecond ends.
 2. The apparatus of claim 1, wherein current supplied tothe reader heater is divided between the first and second planar loops.3. The apparatus of claim 1, wherein the second planar loop ispositioned within the first planar loop.
 4. The apparatus of claim 3,wherein the first planar loop is symmetrical about an axis perpendicularto the ABS and the second planar loop is symmetrical about the sameaxis.
 5. The apparatus of claim 3, wherein the distance between and sizeof the first and second planar loops are configured to control a contactarea of the protrusion.
 6. The apparatus of claim 3, wherein the shapeand placement of the second planar loop are configured to control thestroke efficiency of the reader heater.
 7. The apparatus of claim 3,wherein the first planar loop comprises a second portion that extendsfrom the first end away from the ABS, and a third portion that extendsfrom the second end away from the ABS.
 8. The apparatus of claim 7,wherein the second and third portions extend in a directionsubstantially perpendicular to the ABS.
 9. The apparatus of claim 7,wherein the second and third portions are substantially mirror images ofeach other and first extend in a direction substantially perpendicularto the ABS for a first length and then extend in a directionsubstantially parallel to the ABS for a second length.
 10. The apparatusof claim 1, wherein the first and second planar loops are electricallyand dimensionally parallel to each other.
 11. An apparatus, comprising:a slider having an air bearing surface (ABS), the slider comprising: areader; a writer; and a reader heater configured to cause a protrusionof the ABS at the reader, the heater comprising a first loop having afirst shape and a second loop having a U-shape that is different fromthe first shape, wherein the first and second loops are coplanar andcomprise two resistors in parallel.
 12. The apparatus of claim 11,wherein the second loop is positioned within the first loop.
 13. Theapparatus of claim 11, wherein the first and second loops have a linewidth of about 2 to 6 micrometers.
 14. The apparatus of claim 12,wherein the first loop comprises a first portion that extends from afirst end to a second end for a length substantially parallel to theABS, a second portion that extends from the first end away from the ABS,and a third portion that extends from the second end away from the ABS.15. The apparatus of claim 14, wherein the dimensions of the protrusionof the ABS are determined by the length of the first portion. 16.(canceled)
 17. An apparatus, comprising: a slider having an air bearingsurface (ABS), the slider comprising: a reader; a writer; and a readerheater configured to cause a protrusion of the ABS proximate the reader,the reader heater having a symmetrical shape about an axis of symmetryperpendicular to the ABS, the reader heater comprising a first planarloop and a second planar loop wherein the first and second loops are inthe same plane and comprise two resistors in parallel.
 18. The apparatusof claim 17, wherein the first planar loop has a first shape and thesecond planar loop has a second shape different from the first shape andis positioned within the first planar loop.
 19. The apparatus of claim17, wherein the first planar loop is positioned on a first side of theaxis of symmetry and the second planar loop is positioned on theopposing side of the axis of symmetry.
 20. The apparatus of claim 1,wherein the slider is configured for heat-assisted magnetic recording.